1. Field of the Invention
Example embodiments of the present invention are related generally to a repeater for providing coverage within a wireless communications network and methods thereof.
2. Description of the Related Art
The cellular wireless industry has witnessed tremendous growth in the past two decades. The cell phone has become the most popular personal electronic device, with penetration rates reaching 70-80% in many regions of the world. Even in regions with well developed wireline telephony infrastructure, such as North America, people have begun to “cut the wire” by making the cell phone their only phone. However, conventional cellular networks in North America today are still lacking in terms of coverage area.
For example, the interiors of large buildings often fail to maintain a coverage signal sufficient to support a cellular connection. Also, both downlink (e.g., base station to mobile station) and uplink (e.g., mobile station to base station) signals are typically weakest at the “edge” or border of the coverage area provided by a given base station due to shadowing and/or attenuation. Accordingly, there is a growing need to boost signal strength in these fringe locations, particularly within suburban and rural residential buildings.
Conventional same-frequency repeaters may be used to enhance wireless coverage in problem areas without necessitating a change in the supporting infrastructure. A same-frequency repeater is a bi-directional wideband radio frequency (RF) amplifier with two antennas. A first of the antennas is typically a highly directional antenna pointing to the nearest base station, and a second of the antennas is a broad-beam antenna providing coverage to the desired area. For example, the first antenna may be positioned on a roof of a building and the second antenna may be a strategically placed indoor antenna.
Such a repeater typically requires a precise installation so that feedback received at a “receive” antenna (e.g., an antenna receiving a “donor signal” that is to be amplified, such as from a base station in the downlink or from one or more mobile stations in the uplink) from a “retransmit” antenna (e.g., the antenna transmitting the amplified donor signal, such as to a base station in the uplink or to one or more mobile stations in the downlink) does not cause the system to undergo regenerative oscillation, which is a phenomenon where the gain exceeds the feedback loss (e.g., generating a “loop” which may exponentially increase the signal strength of the amplified, retransmitted signal). Regenerative oscillation may disrupt conventional macro-cellular networks by causing instability.
Accordingly, if high gain is necessary at the repeater, the receive and retransmit antennas are typically kept physically isolated from each other to reduce or avoid the regenerative oscillation. However, because the receive and retransmit antennas must typically be positioned precisely so as to avoid regenerative oscillation by isolating the receive and retransmit antennas, the cost and difficulty of installing a conventional same-frequency repeater may be significant.
Further, conventionally, it is difficult to simply cancel or filter out the feedback signal (e.g., the amplified donor retransmission), transmitted by the retransmit antenna, at the receive antenna, because the feedback signal may not remain constant during operation. And, statically, filtering the feedback signal from the signal spectrum at the receive antenna is not very effective. Accordingly, the gain obtained by a repeater is conventionally limited to the loss of the retransmitted signal on the feedback path such that the donor signal remains stronger than the feedback of the retransmitted signal at the receive antenna.